Cephalopelvic Disproportion (CPD): Causes, Risks, and Management

Cephalopelvic disproportion (CPD) is a condition in which the fetal head is too large or the maternal pelvis is too small (or abnormally shaped) to allow safe vaginal delivery.

Causes

• Fetal factors: Macrosomia (large baby, often from maternal diabetes), post-term pregnancy, hydrocephalus, abnormal fetal position (e.g., brow presentation).
• Maternal factors: Contracted pelvis (android, platypelloid), previous pelvic fractures, skeletal dysplasia, uterine fibroids distorting the birth canal.

Diagnosis

CPD is often diagnosed during labor when adequate contractions fail to produce cervical dilation or fetal descent (failure to progress). Prenatal ultrasound and clinical pelvimetry can suggest risk but cannot definitively predict CPD.

Complications

• Prolonged labor
• Obstructed labor
• Fetal distress (hypoxia)
• Uterine rupture (rare but catastrophic)
• Increased risk of instrumental delivery (forceps/vacuum) or cesarean section

Management

• Trial of labor: Often attempted with close monitoring if no absolute contraindication.
• Cesarean delivery: Indicated for confirmed CPD, failed progression, or fetal distress.
• Future pregnancies: VBAC (vaginal birth after cesarean) may be possible depending on the cause of CPD and type of uterine incision.